Scrambled data streams are well known in the art. There are many types of known scrambled data streams, of which scrambled video streams are in particularly common use.
Scrambled video streams are widely used in conditional access systems. In conditional access systems, as is well known in the art, content, such as video content, is scrambled, and information necessary to decrypt the content is made available only to authorized users. Conditional access systems are particularly well known in the field of television, although conditional access systems are also used as appropriate in other fields.
The terms “scrambled” and “encrypted”, in all of their grammatical forms, are used interchangeably throughout the present specification and claims to refer to any appropriate scrambling and/or encryption methods for scrambling and/or encrypting a data stream, and/or any other appropriate method for making a data stream unintelligible except to an intended recipient thereof.
The term “encoded” is used throughout the present specification and claims, in all its grammatical forms, to refer to any type of data stream encoding including, for example and without limiting the scope of the definition, well known types of encoding such as MPEG-2 encoding. It is appreciated that an encoded data stream is generally more difficult to read, in the sense that more processing and typically more time are required to read an encoded data stream, than a data stream which is not encoded.
The term “complex data stream” is used throughout the present specification and claims to refer to a data stream which is scrambled and/or encoded.
Systems for scrambling television signals, and controlling access thereto, are well known in the art. One such system is described in the following U.S. Pat. No. 5,282,249 to Cohen et al.; and U.S. Pat. No. 5,481,609 to Cohen et al. Scrambled television data streams described in the Cohen et al. patents comprise both scrambled data representing television signals and coded control messages, also known as ECMs. The ECMs of Cohen et al comprise, in a coded form, data necessary for generating a control word (CW) which may be used to descramble the scrambled data representing television signals.
While the two patents to Cohen et al. describe an analog system, that is, a system in which analog television data streams are broadcast to television sets, it is appreciated that similar ECM methods may also be used for digital television data streams. Generally, the scrambling techniques used for scrambling analog television signals such as, for example, the well known “cut-and-rotate” technique, are chosen for their applicability to analog signals. In scrambling of digital television signals other scrambling techniques, well-known in the art, are used, the techniques being more appropriate to digital signals such as, for example, applying the well-known DES algorithm to the digital television signals.
It is also known in the art to apply methods analogous to those used for television scrambling to data scrambling, particularly in the case of digital methods.
A general discussion of some existing data stream playback systems and their drawbacks is found in:
Jim Taylor, DVD Demystified: The Guidebook for DVD-Video and DVD-ROM, McGraw-Hill, 1998, pages 72 and 195.
The following documents from the MPEG-2 standard describe syntax and methods which may be relevant to understanding the present invention:
syntax of a transmitted digital multimedia or other data signal: ISO/IEC 13818-1;
syntax of an encoded digital video signal: ISO/IEC 13818-2;
other methods: ISO/IEC 13818-6.
Other methods relevant to conditional access techniques employing ECMs are described in the following documents:
ETR 289, “Digital Video Broadcasting (DVB): Support for use of scrambling and Conditional Access (CA) within DVB systems”;
TS 101 197-1 V1.1.1 (1997-06): “Digital Video Broadcasting (DVB): DVB SimulCrypt; Part 1: Head-end architecture and synchronization”; and
DVB document TM-1244, revision 3.
Society of Motion Picture and Television Engineers (SMPTE) document 312M, “Splice points for MPEG-2 Transport Streams”, describes “splice points” in MPEG-2 transport streams, which are inserted by a headend to facilitate smooth splicing between steams. Appendix A.6 of SMPTE 312M refers to encrypted streams.
It is well-known in the prior art for known forms of ECM processing, including creating and interpreting an ECM, to take place in a removable security element such as an IC card, commonly known as a smart card.
The disclosures of the following patent applications, assigned to NDS Limited, describe technologies which may be related to the present invention:
1. Israel Patent Application 125141, filed 19 Jun. 1998 and entitled “Advanced Television System”, describes an example of a television system with which the present invention, in preferred embodiments thereof, may be useful. A corresponding PCT International Application claiming priority from Israel Application 125141 was published on 6 Jan. 2000 as WO 00/01149.
2. Israel Patent Application 120174, filed 7 Feb. 1997 and entitled “Digital Recording Protection System”, describes a digital recording system which may be useful in conjunction with the present invention. A corresponding European Patent Application claiming priority from Israel Application 120174 was published on 28 Dec. 1998 as EP 0 858 184 A2.
Methods for providing fast forward/rewind in MPEG are described in an article on the World Wide Web written by Michael Vernick at URL http://www.ecsl.cs.sunysb.edu/˜vernick/ffwd.html, entitled “The Stony Brook Video Server, Implementation and Analysis of Fast Forward/Rewind for MPEG.”
It is further known in the art of data processing to add indexing information to a non-indexed file without changing the basic structure of the non-indexed file. Such files, after indexing, are generally known in the art as ISAM files.
The disclosures of all references mentioned above and throughout the present specification are hereby incorporated herein by reference.